SYMPTOMS

When you publish the Exchange server, you select the Outlook RPC/HTTP(s) option.

On an external computer, a user tries to connect to the Exchange server by using Microsoft Office Outlook.

Note When an external computer uses Outlook to connect to an Exchange server through RPC, the external computer is called an Outlook Anywhere client.

On the Outlook Anywhere client, the user provides the wrong user name or the wrong password.

In this scenario, the Outlook Anywhere client continually uses the wrong credentials every time that it tries to authenticate itself on the Exchange server. The user is not prompted to enter the correct credentials. Additionally, if the Account Lockout policy is implemented in Active Directory, the user account eventually becomes locked out.

CAUSE

This problem occurs because of an issue in ISA Server 2006 SP1. When wrong credentials are used, ISA Server 2006 should return a 401 response that contains a WWW-Authenticate header. However, ISA Server 2006 incorrectly returns a 502 response.

RESOLUTION

To resolve this problem, apply the hotfix rollup package that is described in the following Microsoft Knowledge Base article: